Heat oil in a medium saucepan over medium-high heat. Add carrot, celery, and bell pepper; sauté 5 minutes or until tender. Combine flour and milk in a small bowl; stir with a whisk. Add to vegetable mixture in saucepan; cook over medium heat 3 minutes or until thick and bubbly, stirring constantly. Add oysters; cook 2 minutes or until edges of oysters curl. Stir in chili sauce, Worcestershire sauce, and pepper. Sprinkle with paprika.